Well, fans ate up the BABYLON 5 "Lost Tales" DVD in mid-2007. That was only 75 minutes, and it had a suggested retail price of 24.95.
Of course, for various reasons, that series didn't continue, so who knows how long it could have sustained itself.
If they sold that well... there would have been more.
The economics of Babylon 5
are completely different than Star Trek
, that 75 minute 'movie' probably cost less to make than a single 42 minute episode of Enterprise